The present invention relates to a multiple plate clutch assembly for a power transmission gearing of an automatic transmission and more particularly to a clutch drum for a multiple plate clutch assembly.
Usually, in such a power transmission gearing, after being subjected to a torque multiplication by a torque converter, a rotary power of an engine drives a turbine which in turn drives an input shaft of the transmission mechanism, driving a forward clutch drum within the transmission mechanism during the forward drive. The forward clutch drum has mounted drive plates of a forward clutch inside as splined to the inner surface thereof and drive plates of a high and reverse clutch outside as splined to the outer surface thereof. Thus, the drive plates of the forward clutch and those of the high and reverse clutch rotate with the forward clutch drum.
When fluid pressure acts on a clutch piston of the high and reverse clutch, its drive plates and driven plates are interengaged so that the rotary power of the input shaft is transmitted through the forward clutch drum, the drive plates of the high and reverse clutch, the high and reverse clutch drum and a connecting shell to a sun gear to rotate same.
On the other hand, when the forward clutch is engaged, a front internal gear which is splined to a clutch hub of the forward clutch is rotated.
The known multiple plate clutch assembly is specifically described in connection with FIG. 1. FIG. 1 is a fragmentary sectional view of an automatic transmission illustrating a known multiple plate clutch assembly including a forward clutch and a high and reverse clutch which provide the above mentioned power delivery paths.
Referring to FIG. 1, the reference numeral 1 designates a forward clutch drum which is connected with an input shaft, not shown. The forward clutch drum 1 comprises a tubular portion 4 including a large diameter section 2, a contiguous small diameter portion 3, and an end plate portion integral with this tubular portion 4 closing off the axial end of the small diameter section 3. The large diameter section 2 of the tubular portion 4 has corrugations which define an inner spline 4a and an outer spline, not seen. The plurality of drive plates 6 of the forward clutch are mounted to the inner surface of the large diameter section via the inner spline 4a, while the plurality of drive plates 7 of the high and reverse clutch are mounted to the outer surface of the large diameter section 2 via the outer spline. Slidably received in seal tight manner in the small diameter section 3 of the tubular portion 4 is a clutch piston 8 of the forward clutch. The clutch piston 8 defines a fluid pressure chamber 9 between the piston 8 and the end plate portion 5.
Extending into the tubular body portion 4 is a forward clutch hub 10 connected with a front internal gear, not shown. A plurality of driven plates 12 engaged with a spline 11 of the outer surface of the forward clutch hub 10 are interleaved with the drive plates 6.
Disposed around the outer surface of the forward clutch drum 1 is a high and reverse clutch drum 13 which is connected with a sun gear, not shown. A plurality of driven plates 15 are engaged with a spline 14 formed on the inner surface of the high and reverse clutch drum 13 and interleaved with the drive plates 7.
The reference numeral 16 in FIG. 1 designates a clutch piston and the reference numeral 17 a return spring for this piston.
In operation, when the fluid pressure is admitted to the fluid pressure chamber 9 and thus the piston 8 of the forward clutch is actuated, the drive plates 6 and driven plates 12 are engaged, allowing the transmission of rotary power from the forward clutch drum 1 to the forward clutch hub 10. When the piston 16 of the high and reverse clutch is actuated, the drive plates 7 of the high and reverse clutch are engaged with the driven plates 15 thereof, allowing the transmission of rotary power from the forward clutch drum 1 to the high and reverse clutch drum 13.
Since, in this known clutch assembly, the inner surface of the small diameter section 3 of the forward clutch drum 1 must be finished smooth to receive the clutch piston 8 in seal tight manner, it is impossible to form a plurality of slots or spline on the small diameter section 3. Thus, the drive plates 7 of the high and reverse clutch have to be mounted to the outer surface of the large diameter section of the forward clutch drum 1.
The known clutch assembly has a problem that the diameter of the high and reverse clutch 13, i.e. that of the clutch assembly, is large. Another problem is that the axial length of the clutch piston 16 of the high and reverse clutch is long, thus relatively large waste spaces A and B created between the forward clutch drum 1 and the high and reverse clutch drum 13.